1. Field of the Invention
The invention relates to a collecting device, for attachment to the body and for collecting bodily waste.
Collecting devices for collecting bodily waste, ostomy appliances, wound or fistulae drainage bandages or devices for collecting urine are usually in the form of a receptacle, e.g. a bag, pouch or tube for receiving the waste, connected to an adhesive wafer that can be attached to the skin of the patient. The wafer is typically in the form of a backing layer coated on the skin-facing surface with an adhesive layer and the wafer may further be provided with an aperture for accommodating the body opening. The size and shape of said aperture can often be adapted individually to fit the anatomy of the patient.
One of the crucial parts of such devices is the adhesive wafer. The wafer should be able to fit leak proof around the body opening and have good adherence to the skin without unintended detachment from the skin, but at the same time the wafer should be easy to remove again without damaging the skin. Furthermore, the wafer should be able to follow the movements of the body and be comfortable to wear. The adhesive and the backing layer determine these properties.
When designing a skin adhesive wafer for use in collecting devices, a major issue is to keep the skin relatively dry underneath the adhesive in order to prevent maceration. Maceration occurs when skin is unable to get rid of moisture from transpiration and results in degradation of the skin's barrier function and in bad adhesion.
Usually, skin adhesive keeps the skin dry by being moisture permeable. This allows moisture to be transported through the adhesive from the skin side to the upper side (opposite to the skin), where it is allowed to evaporate. However, this mechanism cannot be used for skin adhesives for collecting bodily waste, as in this case, the upper side of the adhesive is covered by a collecting pouch or is exposed to the inside of the pouch with a relative humidity close to 100%. Therefore, adhesives for attaching a pouch for collecting bodily waste are made water absorbent. Absorbing particles or hydrocolloids (HC) are mixed into an adhesive matrix to absorb moisture from the skin and thereby keep the skin relatively dry. This technique is well known in the art, see for example U.S. Pat. No. 4,551,490 and forms the basis for most of the commercially available ostomy adhesives.
For all such devices, a moisture impermeable backing layer is covering the upper side of the adhesive to prevent moisture from bodily waste inside the collecting pouch to permeate through the backing layer and into the adhesive, filling up the adhesive absorption capacity that otherwise should have been used to absorb moisture from the skin. The backing layers are typically mono- or multi-layered structures containing polyethylene (PE) or ethylene vinyl acetate (EVA). These materials are chosen because they are cheap and they have welding properties enabling a pouch or a coupling ring for a pouch to be welded onto the adhesive wafer. The required mechanical properties of these layers have primarily been that they should have a tensile strength being high enough to withstand the peeling force of the adhesive when removing the wafer.
Efforts have been put into finding a softer film, such that the total device is more able to stretch with the skin substrate of the wearer and thus obtain a more comfortable product. However, absorbing adhesives such as hydrocolloid adhesives are all relatively thick and are stiff adhesives, thus, using a softer film will not influence much on the softness and flexibility of the adhesive wafer, as it mainly will be the softness of the adhesive that defines the softness of the total adhesive wafer and not the softness of the backing film.
With recent development in soft absorbing adhesives, the softness of the backing film has become much more important. At present, it is no longer the softness of the adhesive that sets the lower bar for the softness of the adhesive wafer, but also the backing layer and this puts new constraints on how soft such a layer needs to be.
Thus, when working with wafers with soft adhesives, there are two essential mechanical requirements on the backing layer: It should be soft during wear, i.e. be able to handle small deformations from body movements of about 0-20% and have sufficient tensile strength to carry the peel load from removing the collecting device.
The need for a softer film at small deformations that still has high tensile strength has rendered existing film material less suitable for use as backing layer for such devices. Conventional backing layers can be made thinner to make them softer, but this reduces the tensile strength of the layer to below the strength required for removal. Films with satisfying properties have to be found in other types of materials, these materials can be moisture permeable and the problem of backflow of moisture from the pouch through the backing layer into the absorbing adhesive may suddenly become a problem.
2. Description of the Related Art
Most conventional collecting devices use impermeable backing layers to solve the problem of moisture flowing from the output in the pouch into the absorbing adhesive.
Other conventional adhesive wafers use open non-woven materials as backing layer, but weld the pouch wall to the non-woven in the whole centre portion of the adhesive wafer. This stops moisture from flowing into the adhesive from the pouch, but it also reduces the flexibility of the adhesive wafer, as the pouch material is rigid compared to the non-woven.
Thus, there is still a need for a soft and flexible collecting device having a controlled permeability to moisture.